There are two ways to address this issue.
The first method is to have Percept Research send a “thank-you” message to all survey participants at the end of the data collection period. Using text provided by the school, Percept will send a email message to every respondent that completed the survey. The message would serve as proof of participation in the survey as well as provide specific instructions for claiming their incentive.
Please note that thank-you messages can only be sent after the data collection period closes, and will not be sent immediately upon submission of a survey. The letter of invitation/consent should explain this process to the student as well as tell them when they can expect to receive the thank-you message. Be sure to contact your Project Manager at the beginning of the project if you want to engage this option.
The second method is for you (the survey administrator) to indicate in your pre-alert letter that Percept Research will provide your school with a list of all survey participants so that incentives can be awarded. Percept Research will then provide you will a list of email addresses, in alphabetical order, of all respondents that submitted a survey. Because this option may make respondents feel less comfortable about participating in the survey, using the thank-you message technique mentioned above may be preferred.
Please check out this related topic:
How can we award survey incentives if Percept Research sending the email invitations rather than ourselves?